The idea of a stylus to be bundled with a smart device is something that isn’t new. Samsung has been doing it for years with their Galaxy Note series, and recently Apple released the Apple Pencil, a stylus for the iPad Pro. But styluses currently only work on touch screens. Without the touch screen, there is no meaningful use of the stylus in the outside world.
However, Apple has filled a patent for a pen that can draw on any surface and even in midair. The pen will have be monitored in different ways such as, but not limited to, a force sensor in the tip, motion and orientation sensors, cameras, or an EM triangulation scheme. The data from the pen will then sync with a computer wirelessly to track its location in a 3D environment.
From there, the user can attempt to draw/doodle/write anywhere, and the information will be displayed on the computer. It sounds similar to the 3D print pens which allow people to create small 3D items using a pen that melts plastic, however a digital and more cost efficient version of it.
This is idea is somewhat similar to the concept of AR, with having only certain data viewable through a special lens or a device. The patent was filled in July 2016 and was published in late January. The concept of a stylus to draw something in a 3D plane and then view it through a computer is unique and new, however, currently there a few VR and AR apps that try to do this already.
There is no release date on this pen, or even a confirmation if its an actual product that is being developed inside Apple. Most of the times companies file patents without releasing anything, a common practice done for years.